Ok, so it's not actually a game, but it's an interesting use of Phaser all the same! Just start a piece of music playing (like in iTunes or from a stream) and then click on the interaction in time to the beat. You'll see it generate a nice pulsing wave of graphical effects, which shift around and move in time to your mouse clicks. It's all quite rhythmic!
Color Sounds
Put on some music, click in time to the beat and create some generative art out of it.